1. Field of Invention
This invention relates to a radio or television broadcasting system for transmission of audio and text information and more specially to transmitting digitized audio data and text data.
2. Description of the Prior Art
Numerous systems transmit information on FM radio subcarriers. See for instance, U.S. Pat. No. 5,152,011 issued to Schwob, Sep. 29, 1992. Also known is a single sideband communication system with FM data capability for transmission of analog voice signals. See U.S. Pat. No. 4,852,086 issued to EastmoLd et al., Jul. 20, 1989.
Also known is FM radio sideband broadcasting to specially adapted computers for transmission for instance of news and financial information. Commercially available products available from Mainstream, Telemet, and DeskTop Data broadcast data over FM radio sidebands for receipt by personal computers equipped with special FM radio receivers and software. Typically information is transmitted in digital form, received, and stored in the computer memory for access by the computer user using menu driven software, The data is displayed on the computer screen in conventional alphanumeric form. One product in this category is News Edge, a news service available from DeskTop Data, Inc. of Waltham, Mass. which delivers a number of news and financial information services to a user via FM radio sideband. Software provided with the product scans incoming information and when the incoming information meets parameters set by the user, the information is saved to disk and/or displayed on the computer screen.
These systems have the disadvantage of requiring a personal computer as a platform, and providing information only on a computer screen. The usual computer skills are needed in order to operate such systems, which tend to be quite expensive.
Data can also be transmitted in the Vertical Blanking Interval of a television transmission. The Federal Communications Commission has set aside several lines of the Vertical Blanking Interval for point to multipoint data transmission which may be sold to interested users.
In addition to using the Vertical Blanking Interval, data can be transmitted via a television channel using 384 Kpbs transmission system during the active video portion of the television channel using a system available from WavePhore, Inc. This system piggybacks digital data within the active area of an existing broadcast signal, without interfering with the regular television picture. The decoded data can include text and sound.
An additional channel of communication for data or audio transmission is the Separate Audio Program channel available in television broadcasting.
All of these systems have the disadvantage that the listener or user of the data is restricted to a specific place or time to access the information. The portable radio, be it hand held or in an automobile, also limits the user to accessing only the information that is presently being transmitted.